cheburashka
Senior Chief Petty Officer
- Joined
- May 28, 2005
- Messages
- 715
Correction--a '74. I got the date wrong.
I posted earlier about failing to winterize properly and freezing the water in the block. I've done the pressure test on the water jacket. Seems like the rear welch plugs are ok, because I can pressurize the block and there's decent back pressure. Unfortunately, there's a slight crack in the head between the 1st and 2nd cylinders, right forming a half-circle where the head bolt holds it down. It's not visible to the eye, but when I filled the system with soapy water, I got some minor bubbling and foaming in that area so I imagine the water froze and pushed the head up off of the block.
What's my next step? The head number is 2774531. I assume the old head can't be welded, since it cracked at a load-bearing point. Is that right? I'm unable to test for other cracks, since this one screws up the leakdown test. However, it's a very small crack with just a bit of water seeping through it.
Which Mercruiser heads will interchange? I see quite a few 120s on Ebay, but not so many 140s. Some say they're interchangeable, others don't. How can I tell whether a head will be appropriate for this engine?
I'm not sure the head that's on there is original to the engine. Were 1972 Mercruiser heads hechoed in Mexico? This one was.
The head I pulled has a wide strip between the two central exhaust ports. I've noticed that some I've looked at have a very narrow strip in-between. Would this create a compatibility problem? Does my replacement head have to have a wider strip in between the central exhaust ports so that it will mate up to the exhaust manifold? Is the thinner one what's referred to as "siamesed"?
What are the chances of another crack in the block becoming evident after I've replaced the head? I don't want to throw a ton of money into this old boat and then find out it won't run anyway. Your thoughts?
I posted earlier about failing to winterize properly and freezing the water in the block. I've done the pressure test on the water jacket. Seems like the rear welch plugs are ok, because I can pressurize the block and there's decent back pressure. Unfortunately, there's a slight crack in the head between the 1st and 2nd cylinders, right forming a half-circle where the head bolt holds it down. It's not visible to the eye, but when I filled the system with soapy water, I got some minor bubbling and foaming in that area so I imagine the water froze and pushed the head up off of the block.
What's my next step? The head number is 2774531. I assume the old head can't be welded, since it cracked at a load-bearing point. Is that right? I'm unable to test for other cracks, since this one screws up the leakdown test. However, it's a very small crack with just a bit of water seeping through it.
Which Mercruiser heads will interchange? I see quite a few 120s on Ebay, but not so many 140s. Some say they're interchangeable, others don't. How can I tell whether a head will be appropriate for this engine?
I'm not sure the head that's on there is original to the engine. Were 1972 Mercruiser heads hechoed in Mexico? This one was.
The head I pulled has a wide strip between the two central exhaust ports. I've noticed that some I've looked at have a very narrow strip in-between. Would this create a compatibility problem? Does my replacement head have to have a wider strip in between the central exhaust ports so that it will mate up to the exhaust manifold? Is the thinner one what's referred to as "siamesed"?
What are the chances of another crack in the block becoming evident after I've replaced the head? I don't want to throw a ton of money into this old boat and then find out it won't run anyway. Your thoughts?
